As is known, many household appliances require systems for regulating and controlling one or more operating functions, which are activated or deactivated according to various operating conditions. Such is the case, for example, of a refrigerator compressor, which calls for a control system which, in response to temperature variations measured inside the refrigerator, turns the compressor on or off under the control, for example, of a mechanical thermostat. The compressor supply circuit normally comprises two activating branches, which are active at the start-up (or “launch”) stage and the normal running (“operating”) stage respectively: in which case, a positive temperature coefficient PTC resisting unit is used to regulate current flow through the launch branch, and the mechanical thermostat for regulating current flow through the operating branch.
A major drawback of control systems of this type is the relatively high energy consumption involved, which is mainly due to the presence of the continuously operating PTC unit, and to the difficulty in regulating the mechanical thermostat.
Employing an electronic as opposed to mechanical thermostat and other types of relays in place of PTC units permits a certain, albeit relatively small, reduction in consumption, but calls for the use of more complex, more expensive components.